There is a sentence that many people take home with them after a visit to the doctor: "Your blood values are within the normal range." And that often means: all clear. Everything is fine. But what exactly is this normal range for blood values - and whose norm is it actually? The answer is less clear than we would like it to be. Behind every reference value is a story of statistics, conventions and sometimes tangible conflicts of interest. Anyone who knows this story begins to read laboratory values with completely different eyes.